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How much fuel does an A380 hold and where?
How much fuel does an A380 usually carry (in litres) and what is the maximum? How much is in each wing? How much is in other fuel tanks and where are they?

I think this question qualifies for "this question doesn't show any research effort" and could be downvoted.

The "where" part is answered here: Is the entire length of a B747 or A380 wing used as a fuel tank?

The total capacity of fuel tanks of Airbus A380 is 320000 liters.
The fuel tanks in Airbus A380 are shown in this image.

Image Source
The capacities of different tanks are1 (in liters):

Tail tank: 23,698
Inner tanks: 90,600
Mid tanks: 72,000
Feed tank 2 and 3: 28,130 each
Feed tank 1 and 4: 26,974 each
Outer tanks: 9,524 each

1 The only place I found this information is in the book Airbus A380: Superjumbo of the 21st Century. Luckily, it is on Google books. This excerpt from the book about the relevant information says:

The horizontal stabilizer runs through section 19 and includes an integral fuel tank between ribs 8 left and right. The fuel level in the tail tank, which can take up to 23,698 liters, is adjustable in flight for trimming purposes. Overall, the hard-line A380-800 fuel-tank capacity is 315,292 liters, most of which is contained in two inner tanks with more than 90,600 liters. Two other mid-tanks hold about 72,000 liters between them, with inner engine 2 and 3 feed tanks containing 28,130 liters each. The outer engine 1 and 4 feed tanks each hold 26,974 liters, while the two outer tanks each hold 9,524 liters.

Just to complete the information, that is the configuration for an A380-800. If the -900 and -1000 were done and not abandoned, they will have center tanks (2 of them) in the central box of the wings.


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What design features or systems help to prevent a hard nose landing?
Pilots perform perfect manual landings almost all the time with the nose wheel touching down softly and elegantly. When landing an aircraft of any size really more so for the jumbos and super jumbos, this seems like an incredible feat given their weight and the speed at touchdown.
Apart from training, what design features or systems aid the pilot in achieving a soft nose wheel touchdown? Are there any features to help pilots in the event of an accidental abrupt push of the yoke during touchdown?

The elevator, mostly.

And the pilot of course.

Note that while the weight might be big, most of it is supported by the main wheels. The nose wheel only supports about 2–4%.

The longitudinal stability of the aircraft.
Aircraft are designed so that at any given elevator position they maintain a corresponding angle of attack¹. Any decrease in AoA creates pitch up moment to increase it and vice versa.
At touch down the pitching moments change a bit, but the general tendency remains, so without change in the elevator position, the plane will tend to keep the nose wheel off the ground. The nose only touches down when the pilot eases the back pressure on the control column, or the plane slows down enough that the elevator efficiency decreases below what is needed to keep the attitude.
The pilot just has to ease the back pressure gently and not slam on the brakes until the nose wheel is on the ground, because brakes do generate significant downward pitching moment (this applies to all vehicles; you can feel it in a car quite well).

¹ except modern fighters, but there the control computer emulates that behaviour, otherwise they wouldn't be controllable.

Does your footnote imply that modern fighters are not designed? ;)

While Jan Hudec’s answer is certainly correct, I think some credit should be given to devices like flaps and vortices generators that improve flight characteristics with higher angles of attack. Without them, pilots would have to land faster, with a more nose down attitude, which would make it more difficult to set the nose down softly.

Without flaps, aircraft would land faster, but generally with a nose higher attitude, because flaps increase the lift, but reduce the maximum angle of attack.

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Would pressurised air holes on supersonic aircraft mitigate the heat problem?
Would air holes or tubes of 50mm diameter blowing pressurised air outside the surface of a hypersonic or supersonic aircraft mitigate the problem of heat? They would be placed such that when they blow, there is no surface of the aircraft skin colliding directly with the air outside when the aircraft is travelling at supersonic or hypersonic speeds.
In areas where lift and control is required, they'd blow at a lower pressure and leave just enough enough air colliding with those areas for them to function.  Would this mitigate the sonic boom?

Where would this air come from?

bleeded from an engine installed for that purpose or leaving the or one of the engines that powered the aircraft to scramjet operating speed on depending on the aire needed

That's not a bad idea, some torpedoes work like that in water and move at 200 kt.

seems people are downvoting my questions related to innovation.  Is innovation and invention not desirable in this site and most importantly in aviation?  Then somebody should start and Aviation innovation SE

@mins would such a system mitigate against sonic boom and all forms of drag?

@securitydude5: While the idea is not frivolous, that doesn't mean an answer can be provided without months of research. Unfortunately industrialization of ideas is not a simple task as you seem to assume most of the time.

Are you innovative?  It seems like you are not familiar with aero-engineering (how do flight controls work? how are wings configured? what does the yoke do?) making up non-existent problems, throwing out random, unsubstantiated ideas, and asking other people to do the work of figuring out if they're any good.

sometimes I ask questions that may be of interest to everyone, but I like to think of myself as an inventor innovator type. Thanks for the answer by the way, greatly appreciated

You've asked 30 questions in the last 15 days, and most of them have been heavily downvoted.  Perhaps you should reconsider the questions you post?

I will but they are pressing questions for an inventor innovator type

There should have been a system-generated Question Ban on this user days ago. That he is still asking questions is clear evidence that the parameters for when a question ban goes into effect need to be revised.

@securitydude5 While I thought this question had a bit of an interesting premise, I would heavily recommend you get some good books on aerospace engineering (or engineering in general), and a book on thermodynamics. This way, your future questions can be based on real challenges in engineering. You can't be innovative if you don't know the current state of the art!

The idea of using small air holes to cool a surface is not completely 'out there'. In turbine engines, the turbine blades are cooled by blowing bleed air from a compressor stage over the blades.
Here, cooling with bleed air makes sense, because the air in the turbine is hotter than the compressed bleed air, due to the added energy from fuel combustion.
However, it would not work to cool from a supersonic shock. The reason for this is the ideal gas law. Specifically, we're going to look at a reversible adiabatic compression. This is the compression of a gas, without any heat exchange with the environment. Due to adiabatic compression, the temperature increases as follows:
$$ T_{end}=T_{env}+\mu ( P_{end}-P_{env})$$
with $µ$ the Joule-Thompson coefficient, which for air has some positive value. The key point from this equation is that the final temperature is only dependent on the pressure increase.
A supersonic aircraft creates a shockwave in front of the aircraft. This shockwave is a sharp increase in pressure, resulting in a sharp increase in temperature. This rise in temperature is what heats the aircraft.
The 'protective' air film you think of, must have a higher pressure than this shockwave - else, air is going in rather than out of the holes. Using the above equation, this means that the air going out of the holes must have a higher temperature than the shockwave. Your idea only makes your airplane toastier!
The only solution is to change from an adiabatic compression to a more complicated thermodynamic cycle: most likely, adiabatic compression in the aicraft engine, followed by isobaric (constant pressure) heat exchange with the environment. Heat exchangers, however, are heavy, bulky structures, and are avoided as much as possible. In fact, passenger airplanes first compress the air to a much higher pressure than needed, to artificially increase the temperature; all in an effort to reduce the heat exchanger size.
Assuming you have a heat exchanger made from handwavium, we can turn to your control surfaces. The outside air doesn't care whether they hit a solid surface or a film of air - the shockwave creates just as much of a pressure differential, which is what creates the force on your control surface. In fact, a shockwave is often situated a little bit in front of the surface, because there is some 'trapped air' behind the shockwave. You may need to increase the pressure of your air holes at the pressure side of your control surface, so the system must include some control valves.
The sonic boom is still exactly the same. A sonic boom is just 'air couldn't get out of the way quickly enough'; it doesn't matter whether it needs to get out of the way of a solid airplane or a thin air film.
I can't imagine why your holes should be 50mm - that's huge. You want the holes to be as small as possible. This way, you can put them as close together as possible, so that each bit of aircraft skin is close to a hole, and protected by a film from that hole. Think of it like this: what does the middle of a hole contribute to the cooling of the neighbouring skin?

Well, theoretically you can compress the cooling air in stages with intercoolers between the pressurization stages. This even reduces the work needed for pressurization and produces (relatively) cool, pressurized air. Obviously, this now shifts the problem to finding a heat sink onboard.

@Peter An intercooler would need a heat exchanger as well, and a relatively big one as the temperate at intermediate stages is less high. But of course everything is possible at a military budget...

I disagree that a "heat problem" even exists.
The Concorde, a supersonic passenger jet, faced a peak temperature of 153°C (307°F), and that is only over a tiny part of the nose.  (source)
Even though that sounds like a lot, it is about the right temperature for baking muffins in a kitchen; a typical pizza bakes at 425°F.  No one would say my kitchen has a "heat problem".
Even for extreme planes like the SR-71, heat is pretty easy to manage, and not really a concern that needs an entirely new system of airholes, tubes, inlets, valves, sensors and controls to deal with.
You have a solution in search of a problem.  The problem does not exist.

No heat really is a problem at high speeds as it degrades the yield strength of the airframe structure.  This requires the aircraft to be overbuilt, adding hundreds if not thousands of extra pounds of structure onto the aircraft, decreasing its useful load.  The other solution is to use exotic alloys and composites, which drive the costs through the roof and have other problems with an immature material.  Past Mach 2.5 heat is a major factor for aircraft design, especially getting into hypersonic or runway to orbit aircraft.

To cope with the heat, special heat-resistant aluminium alloys were used on the Concorde. This should prove that heat was indeed a problem.

The SR -71 had to use titanium, expensive and hard to machine, which was very novel at the time are required considerable research. Also, the thermal expansion of it is so great, it leaks fuel on the ground. So, saying "heat was pretty easy to manage" on the SR-71 shows you haven't read about it much at all.

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Do horizontal stabilisers provide any lift?
Do jumbo and smaller airliners' horizontal stabilizers provide any lift? Apart from maintaining the aircraft's angle of attack, can they perform the dual function that includes adding some lift as well? Are there any aircraft designs that use horizontal stabilizers for lift as well, apart from delta wing aircraft?

I don't know about airliners, specifically, but I am just about certain that I have seen it stated that a stabilizer may produce lift at low speed, particularly with the C of G aft (but still within limits), but I cannot find the reference. The context was with respect to sailplanes: the author was explaining that this is not the benefit it might seem (and certainly not worth aiming to achieve an aft C of G for) because this lift comes at the cost of a higher drag than if it were generated by the wing.

This question cannot be answered without leading into debate. Even if you ask different university professors you get different answers. Most people think the stabilizer only creates down forces (as you can see down below), which is what they have been told again and again but this doesn't make it any more or less correct. All I know is that the math also allows for the stabilizer to create an upwards lift with the aircraft still being stable and controllable and depending on the flight situation you can have significant positive lift.

@sdenham: If the lift is in proportion to the respective aspect ratios, moderate tail lift will indeed produce the lowest overall induced drag. That is what good competition glider pilots aim for. Your run-of-the-mill weekend glider pilot will be more comfortable with neutral to slightly negative lift on the tail, however. Here is where you might have read about positive tail lift.

@PeterKämpf Thanks for the link, though that's not the reference I am thinking of. I think it was from a blog post from, or hosted by, a German sailplane manufacturer - maybe Glaser-Dirks, and it might have been a predecessor to this one: https://www.dg-flugzeugbau.de/en/library/optimum-cg-sailplanes

@qqjkztd: Certainly positive lift. The canard glider would use a high aspect ratio canard with plenty of camber.

"Are there any aircraft designs that use horizontal stabilizers for lift as well?" -- absolutely-- see related answer "https://aviation.stackexchange.com/questions/22087/do-any-airplane-designs-exist-that-dont-involve-a-flight-surface-that-provides/76837#76837

The horizontal stabilizer provides lift, but usually in the negative direction.
Could one provide positive lift?
The answer depends on cg location.
Forward CG, the answer is no.
Aft CG, the answer is yes but only if the CG was aft of the center of lift.
In other words, the more forward the CG is compared to the center of lift, the more downforce the tail must provide.  The lift from the horizontal stab in the "wrong direction" must be countered by the wing, and thus there is more induced drag.  For a given aircraft gross weight and thrust/power, there will be a higher cruise speed with a more aft CG.
There are practical limits to extreme fore and aft CG positions, and so each aircraft has an allowable "envelope" for loading for safety margin.
Aircraft are designed to have a range of allowable CG locations to make loading easier before the flight (especially for cargo aircraft), and also to allow for passengers & crew to move about the cabin in flight.
Horizontal stabilizers could be sized smaller but that would decrease loading flexibility, decrease passenger comfort, and decrease aircraft handling performance; often all airfoils and control surfaces are designed with many factors in mind, for good control harmony, good ride in rough air, for stability on instrument approaches, for flexible loadings of various belly and main deck cargo holds / passenger configurations, etc.
Flying wings and delta wing designs come to mind as aircraft without horizontal stabilizers, such as the Northrup Spirit or Convair Delta Dart.
Your other question, would manufacturers design horizontal stabilizers to provide lift?
Hopefully you can see by now this is not a design goal.  Wing design is so advanced that designers are making amazingly beautiful and high-performance wings that are most efficient at creating lift.  Look at a Gulfstream V wing or Boeing 747 wing.  It is not efficient to create a wing that doesn't work great and then needs an additional surface to help make more lift.  Exceptions to that might be bi-planes or tri-planes, as they used several shorter wings instead of 1 longer wing, but that is not practical in air transport.  How many Boeing Biplanes and Airbus Triplanes do you see traveling the globe? It's simply better to put all the lift needed into a single wing design.

To increase pitch, the tail provides a certain amount of down force (lift vector pointed down toward Earth). To decrease pitch, the tail provides less down force, but it is still negative lift. For a transport category aircraft whose load factor limits are +2.5g and -1.0g, there is hardly a need to have positive lift coming from the tail.

As a general rule, if the small surface is forward of the main wing, it lifts up.  If it's aft of the main wing, it lifts down (most of the time).
This is a gross oversimplification, but it's very useful to help with imagining what is going on in your mind.
An airplane with a normal tail is like a seesaw, except the pivot is not a solid point, but the middle of the lifting force generated by the wing.  One end of the seesaw has the center of gravity trying to tip it forward, like a kid sitting on the seat, and the other end is you pushing down to hold the kid up, or in the airplane's case, the horizontal tail pushing down against the moment of the center of gravity acting forward of the center of lift, to keep it in balance.   If you broke off the horizontal tail, the airplane would point straight at the ground, as if you let go of the seesaw seat on your end and let the kid drop.
An airplane with a canard surface at the front and a large wing at the back is more like a dump truck.  There is a big axle at the back holding most of the weight, and a little axle at the front holding up a minority of the weight.
Both axles are holding up - and both the canard airplane's surfaces are lifting, but the ones at the back are doing most of the actual work.  The center of gravity is close to the end with big axle (the main wing), and the axle at the front end (the canard surface) only doing a small portion of the total holding up (or lifting) because its job is mostly about control (control over pitch and speed in the airplane, control over steering and braking in the truck).
Airplanes with three surfaces, both a tail and the back and a canard on the front, are kind of like a seesaw but with a little support stick under the kid to help hold him up so you don't have to push down as hard at your end (the tail).  Kind of a seesaw/dump truck hybrid you might say.

is it not possible to have adesign that moves the wings a bit forward to the point the horizontal stabilizers are not necessary?

Yes, sort of...they are called flying wings and they use special airfoil shapes that are naturally stable in pitch by generating the "seesaw" balancing downforce right at the trailing edge.  It's the same balance of forces, just all done within the wing chord.  Since the seesaw balancing act is being done over an extremely short arm - the trailing edge is a lot closer to the center of lift than a tail out back, the center of gravity range is very restricted and they tend to be very touchy to control in pitch. That's why you don't see them all over the place. Good configuration for gliders tho.

An aircraft with a conventional (tail) horizontal stabilizer is designed with the CoG forward of the centre of pressure - a nose-down force. The stabilizer provides a 'downward'-acting force on the tail (opposite to the lift generated by the wing) to oppose and balance the nose-down force.  This provides pitch stability: it returns the aircraft to its original pitch when it has been perturbed by a nose up- or down- force such as would result from turbulence.  Without this damping mechanism the plane would be pitch-sensitive to the point of being unflyable.

Any canard design will use the horizontal stabilizer for lift.
Airliners historically used downforce on their tails in order to have sufficient static longitudinal stability, but the more recent designs use a small amount of lift in cruise and keep stability up by artificial means. A tail tank is sometimes used to shift the center of gravity sufficiently back.
Tail lift in trimmed flight varies when a cambered airfoil is used. Wings using cambered airfoils will usually result in positive tail lift at high angle of attack and moderate to rear center of gravity locations. Usually, the loading of the tail should be low in order to allow for enough margin for maneuvering.
Note that the negative airfoil camber at the root of a tailplane helps to keep the isobars on the sweptback surface parallel up to the root, so this is not immediately an indication of predominantly negative tail loads. Negative nose camber on the tail also helps to delay flow separation on the tail at high negative loads, which are needed to trim the aircraft with full flaps.

For stability reasons tails generate a down force.
It would in theory be possible to have a horizontal stab generate lift (upward force) by compensating for the resulting instability with a fly by wire system, but the wing/tail system would always be less efficient at generating lift then just making the main wing a little bigger.

This is an old and hard to dispel misconception. I had airliner pilots insist on it, but it is still wrong. Stability with positive tail loads is possible - all you need is less lift per area on the rear surface.

I agree that for longitudinal stability that the CG must be forward of the center of pressure CP. But you also need for stability that when the angle of attack of the main wing = 0, the moment about to the CG must be positive. Otherwise you have a lawn dart. To get this, you need downward force on the tail when the main wing is at zero lift. For sure the tail will be generating downward force in a stable configuration for at least some flight conditions. Haven't thought it through beyond that.

Of course you have a downforce on the tail if the plane is stable and the wing is at zero lift. How else would you satisfy the condition of less lift per area on the tail? But most of the times the wing produces considerable positive lift - that is what it is designed for. This leaves enough margin for some positive lift on the tail, too. And if the center of gravity is ahead of the center of pressure, the aircraft will pitch down. Both have to be at the same lengthwise location for straight flight.

The opposite.  Generally the tail pushes down on the aircraft. While the wings push the fuselage up,  the horizontal stabilizer pushes the tail down.  Yes, this does increase load on the wings.
Look closely at the airfoil on a horizontal stabilizer, you can see it is inverted.
Also, if you look at the range of motion on fully movable horizontal stabilizers on jetliners, the vast majority of their range is negative AoA.

Source

Lift is lift.  It acts roughly perpendicular to the chord of an airfoil; to which side of that chord line depends only on the airfoil and angle of attack.  What you call 'anti-lift' is lift generated by the horizontal stabilizer that acts 'downwards' (toward the lower surface of the airframe) in conventional flight.  The lift is not affected at all by the aircraft's orientation relative to gravity.

@a.out okay....

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How does the Blackbird SR-71 pressurize the cockpit at Mach 3?
I'd assume the Blackbird's engine that converted into a ramjet once at supersonic speed had no moving parts at ramjet phase. If the engines were off, how then did it pressurize the cockpit at cruise altitude to ensure pilot safety and that he/she did not pass out from lack of oxygen?

The SR-71 used the P&W J58, which is full of moving parts, and works very similar to a typical jet engine.  Your assumption that it has no moving parts is wrong.   While the engine RPM did slow down at maximum speed (up to 90%), it never stopped, and always generated enough power for electrical systems, pressurization, hydraulics and any other needs.
While the cockpit was pressurized (but sometimes only to 26,000 ft. pressure-altitude), the two-man flight crew wore full body flight suits for warmth and oxygen.

does a ramjet have moving parts?

The J58 (as modified for the SR-71) is only a partial ramjet.  The core slowed, but never stopped.

As I understand it, it simply used large bypass ducts that went around the core and fed the afterburner with ram air.

@securitydude5 A pure ramjet has no moving parts, but the J58 was a hybrid engine that had a normal turbine core and bypass ducts around it.

At no time was the J58 a pure ramjet.  Above Mach 2, air is diverted around the burners & turbine directly from compressor stage 9 outlet to the afterburner inlet.  http://dtstapp.blogspot.com/2014/12/thrust-and-design-analysis-of-j58.html

@securitydude5 does a ramjet have moving parts? is a separate question, and one which can be easily answered by reading the wiki article on ramjets.

@jules its a rhetorical question

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What happens if I cross the ADIZ line without a flight plan and no clearance or contact with ATC?
I'm on a flight to/from the Caribbean on a single engine Cessna and I crossed the ADIZ (Air Defense Identification Zone) line.  I haven't filed a flight plan, I don't have clearance from ATC, and I'm not in contact with ATC.  I do have mode c transponder active on ALT and code is 1200 (VFR) and my altitude 6500 ft MSL.
The ATC would see the aircraft, its altitude, and its velocity.  Based on this flight data, ATC would most likely conclude this was an ignorant or lost pilot or lost drone, and no threat posed.  Have there been any instances where military or coast guard air craft were actually sent for  interception of such small and slow aircraft?  What are the statistics on this?  What would the fines and penalties be?  I'm assuming this would apply more when entering the US ADIZ than exiting.

Most likely you are going to be intercepted by military fighters to determine who you are and your intentions.

"In most cases, would military or coast guard air craft really be sent for interception" is somehow calling for opinions.

In the late 60's, in a C152. I flew a guy, at a low altitude out of Key West to the Marquessa Islands area to look for sunken Spanish galleons.  On the return trip I was nervous flying at 200 feet above the ocean and climbed up to 3,000 feet.  After a few minutes al said altitude my windscreen flashed black. A F-4 had come from behind and below - zoomed up a few yards in front of me! Looking behind me I saw his wingman, gear and flaps down, S_turning on my six.
A quick call to FSS clarified the situation.
That is what happened to me upon inadvertent entry into the ADIZ. I don't expect it has changed.  There were no followup actions other than the echos of the F-4's pilots laughter.

Which Marquesas?  https://en.wikipedia.org/wiki/Marquesas_Islands

The entire point of an Air Defense Identification Zone (ADIZ) is to notify pilots that the relevant defense forces require identifying all aircraft to determine whether they are a threat.
They much prefer to do this via you filing the appropriate flight plan and talking to ATC/FIS. If you don't do that, you should expect to be intercepted by said defense forces for identification, and you may face civil or criminal penalties for making that necessary. If you do not comply with the intercept procedures and they genuinely believe you are a threat, you may even be shot down.
In the US, exact penalties for aviation offenses are not specified by law, so the FAA can impose anything from a slap on the wrist up to permanent revocation of your license, with their choice (at least in recent years) for a first offense depending largely on whether you admit you were wrong and agree to remedial training so it doesn't happen again.
I haven't run across any statistics on ADIZ violations, but interceptions happen frequently for clueless VFR pilots violating TFRs, the DC FRZ/SFRA, Resticted areas and Prohibited areas.

Important clarification: the US does not mandate that foreign aircraft not intending to land on US territory file a flight plan or even respond to identification requests: https://2009-2017.state.gov/secretary/remarks/2013/11/218013.htm. Otherwise their fight against the Chinese ADIZ claims would be undermined.


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If unable to procure Helium, are there any regulations against filling lighter than air craft with Hydrogen instead?
The price of helium is going up again, and it is very difficult to find suppliers without established contracts.  If all possible safety measures are taken, are there still regulations by FAA or other that would prohibit use of hydrogen instead for buoyancy in lighter than air non-thermal aircraft?
The causes of the Hindenberg fire are well documented and studied so lessons learned such as sudden grounding when aircraft surface has accumulated significant electrostatic charge can be avoided through measurement and continuous static dissipation techniques used on current aircraft.

Trying for the Darwin Award?

The Hindenburg did fly successfully for 14 months before the fire destroyed it, so chances are you do have some up-time. Possible items of interest: an article in The Economist and an answer on the SE Aviation site

If you decide to do this please do so far away from me. Or anyone else.

In these times of widespread fears and precautions, using hydrogen as a lifting gas is completely out of the question. The real risk involved, however, can be estimated by remembering the long history of hydrogen-filled balloons and airships. Of course there have been cases of fires and explosions due to that gas, but most accidents were not hydrogen-related, but to bad weather, structural failure, human error, or engine trouble.

The balloons in the Coupe Aéronautique Gordon Bennett use hydrogen. It's not out of the question. http://www.fai.org/fai-slider-news/42015-10809id-qaa-what-is-the-gordon-bennett

yes, it is not uncommon to use hydrogen. esp folks trying to get more gas balloonists, helium is pricy and one flight is cost prohibitive for the average person.

The Hindenburg utilized aluminum flake in a nitrocellulose impregnated fabric.  Materials have improved since then.
In the case of He, diffusion is inhibited by polar surfaces.  For the He to diffuse through the membrane in a balloon, it has to disolve into the fabric layers prior to a barrier such as aluminum. I understand that lithium and beryllium foils have higher impermeability.
In the case of He, poly(ethylene terephthalate) is a reasonable barrier, and PET is commonly available in films (and soda bottles).  It is rather polar, and serves to reduce solubility.
H is a different bird, in that it has low polarity, and different materials will aid in reduction of solubility. Butadiene-acrylonitride co-polymers have low polarity and may perform better with a low polarity gas such as H2.
The gas envelope questions are really materials science questions, and require a fair understanding of not only the mechanical properties, but even more so of the permeability, solubility and diffusivity of the copolymer you might consider.
The legality of using H2 rather than He2 may not be an issue, but even if it were, I am sure that waivers are possible.
A quick check of regs on gas balloons indicates that hydrogen may be used if the aircraft manufacturer approves the gas.  So it appears there is no hard regulatory bar.
Checking with a source at NWS, who indicates their balloons are launched with H2.

Can you give a citation for the relevant regulations?

See third paragraph for guidance wrt H2, He2 and other gasses.   https://www.faa.gov/aircraft/air_cert/design_approvals/balloons/  The meat is in 14 CFR 31 which is airworthiness standards.  14 CFR 31.33 is suitability of materials. The manufacturer of the gas balloon will have limitations as to the gas(ses) that are approved for the envelope material.

addendum, as well as the lift, etc.  Since they have to test various materials, they may be disinclined to do extensive testing with gasses which are intrinsically incompatible with their envelope, or they could have an offering of an optional envelope suitable for other gas(ses).

The Hindenburg utilized aluminum flake in a nitrocellulose impregnated fabric. Actually, nitrocellulose was rejected in favor of cellulose acetate butyrate due to the former's known flammability. The aluminum was a powder, not flake, and was in low concentrations in the doping emulsion. The Hindenburg's skin was flammable, but not particularly so. Even after the intense fire there were portions of the skin that were unburnt.

@TomMcW I confirmed my sources and then did a few more searches on the construction materials and techniques. While there is substantial differences in reporting, I am inclined to agree with what you report. Thanks.

@mongo There's a lot of junk-science and misinformation out there about the H'burg. People who are trying to promote hydrogen power run into the knee-jerk H'burg comparison. The two are not the same but public perception is that hydrogen=boom. So the H ppl try to make the case that H wasn't responsible for the fire. They make specious claims about the skin material or that it was doped with rocket fuel or thermite, counting on people's lack of chemistry knowledge. They try to get people to ignore the famous film clearly showing a ship burning from the inside out.

If you can manage to make some He2 to use in an aircraft as you suggest, I'll be extremely impressed. But it would be a bit pointless, since it would be twice as dense as regular old He.

@Mike Scott, yup, pretty funny.  Asleep at the bond and anti bond. He He He

Of course, the NWS's balloons are not (to the best of my knowledge) manned.

Hydrogen and Helium are quite different substances, you are likely going to need gasbags made of different materials to prevent (or at least limit) leakage through the sublimation of gas through the material.
So even if it is legal, it still isn't practical (and given that it's a massive safety risk my guess is it wouldn't be legal).

I was thinking that Helium was actually more of a problem, since Hydrogen would typically be in the from of the molecule H2

@EugeneStyer an H2 molecule is smaller than an He atom, and can more easily penetrate fabrics and plastics.

And... then there's that whole violently explosive thing...

@jwenting, what size are you using for a H2 and He2 molecule?  The van der Waals radius is 120 and 140 respectively, approximately. That's not a big difference.  Permability of a membrane is about the chemistry and materials properties much more than the molecular size.

@SnakeDoc The Hindenburg exploded because of the gasbag coatings, not the H2. Ref: http://web.archive.org/web/20131102010145/http://www.h2carblog.com/?p=339

@RoyTinker While you are correct, H2 gas is highly combustible and easily set off. Just about every high school chemistry glass has witnessed just how easily set off H2 gas is. https://www.youtube.com/watch?v=zX9x0piJ_Vo

@SnakeDoc: Yes, that's true. Here's a video of the Hindenburg disaster: https://www.youtube.com/watch?v=CgWHbpMVQ1U. That's an H2 fire.

Would there be any regulatory consequences of incomplete inflation of a flexible craft by using hydrogen? Hydrogen is approximately 10% more buoyant than helium, therefore the lift factor will be met before the design shape of the craft is reached. Or is this negligible with balloons, as it would be for rigid dirigibles with discreet internal ballonets?.

@Mackk: Rigid dirigibles don't have ballonets.


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Why does the Zapata Flyboard Air UL consume so much more fuel/hr than the Mosquito Air?
They are both ultralight and abide by FAA ultralight reg 14 CFR part 103.  The Mosquito Air is an ultralight 1 person helicopter whereas the Zapata Air UL is a micro jet turbine powered 1 person ultralight hoverboard. They weigh the same and both only carry 5 gallons of fuel as this is dictated by part 103.
The 5 gallons will last 1 hour of cruise flight time on the Mosquito while only 8 minutes on the Zapata.  Granted we are dealing with different technologies here and different fuels (Zapata uses kerosene, Mosquito uses avgas) I was surprised by the fuel burn difference.
The bare physics tells us that equal masses should require the same amount of thrust, thus energy, to hover in place where lift equals weight.  Kerosene has similar energy density to avgas.  And, a jet turbine is supposed to be much more efficient than a 2-stroke, 2 cylinder gasoline engine.
The Mosquito boasts of a 64hp engine "with the highest power to weight ratio on the market today".  The Zapata company seems not so much concerned with the gas guzzling fuel consumption.  The 2 companies seem to have different priorities here, so I'm guessing the fuel efficiency of the Zapata could be improved.  Still, this is a huge difference that is difficult to understand.

Powered lift burns a lot of fuel.

" Kerosene has greater energy density than avgas". Source please.  Everything I can find says the opposite.

@Simon  Gasoline is primarily the 5 carbon hydrocarbon pentane that vaporizes easily and is less dense than the long carbon chain hydrocarbons that make up kerosene.  Kerosene, JetA, and diesel are very similar in energy density and composition with less than 1% difference between them.  I don't think you are disputing that diesel has a higher energy density than gasoline.  Raw pentane is not energy dense enough so the 8 carbon hydrocarbon, octane, is added so we have an octane rating.  100LL is 100 octane rating with Lead compound added, which could be similar energy density to kerosene.

@Simon I will open this topic as a separate question.

@Simon  you are correct, my bad, corrected question.

@simon Kerosine has the higher energy density, gasoline has the higher specific energy. When comparing the endurance of a 5-gallon tank, the former is more relevant. https://en.wikipedia.org/wiki/Energy_density#Energy_densities_of_common_energy_storage_materials

@sdenham 100LL is not listed in the wikipedia chart.  The very high octane rating surpasses kerosene in both energy density (energy/volume) and specific energy (energy/mass) by about 5 to 10%.

@0tyranny0poverty I am finding it surprisingly difficult to find a source stating a number for 100LL explicitly - the one I have found references a primary source saying "aviation gasoline" gives ~31 MJ/L (over10% less than the generic gasoline figure in Wikipedia). While this publication seems to mostly use "aviation gasoline" to refer to 100LL, it is not definite. (NB: the publication also spends some time on the fact that the specific energy and energy density of hydrocarbon fuels are generally inversely related.) What's your source?

It's the difference between jet engines and propellers. It is a lot more efficient to accelerate more air to a low velocity, than it is to accelerate less air to a higher velocity. For fixed wings, the only reason to use jets is if propellers hit their speed limit, when the tips break the speed of sound.
Hovering flight is particularly demanding on fuel consumption. The Mosquito Air burns through its fuel a lot faster than 1 hour when it stays in hover all the time. Cruising in a helicopter makes the fuel consumption  a bit more similar to fixed wing: the rotor blades start to act more like wings and can use airspeed to reduce induced drag. Still less efficient than fixed wing cruise, but more efficient than helicopter hover.
The Zapata Air UL is always in a hover, and has no wings, and is a jet. It never gets the increased efficiency effect of forward flight that a rotor gets. And jets are really very inefficient at low speeds!

It's a pretty cool device though.

the statement about the air velocity clarified my mind fog.  E = 0.5mvsq so more air mass at lower velocity is easier than less mass at higher velocity since we are dealing with velocity squared.

Yes, thrust = $ \dot{m} \cdot (V_e - V_0)$

Could you put wings on the Flyboard?

not part of the design

my current body weight would be above the useful load of either craft even with half tank of fuel, so I need to get one that runs on bicycle pedal power if such a thing exists and burn off those pounds:)

@Otyranny Opoverty like this one?

I would still be too heavy to get off the ground. for the first month of pedaling anyway.

First, let's compare apples to apples, and compare the Flyboard to the Mosquito XET, the gas turbine powered version. The Mosquito XET with it's 90hp Solar turboshaft engine consumes around 8.5 gph, while the Flyboard with six small turbojets is more like 38-40gph.
Aside from the greater efficiency of propellers over pure jet exhaust, also consider that the XET has a single gas turbine engine, while the Flyboard has six much smaller gas turbine engines.
Gas turbines are more efficient when they are made larger, which is the primary reason that large twin engine airliners are pushing out four engine airliners for international travel. Far more efficient usage of fuel, now that the larger twins are getting ETOPS certification.

I know this post is a little old, but I happened to find this post while trying to find out what turbines Zapata uses.  There seems to be a misperception of how helicopters fly/hover compared to how a turbine engines produce thrust.
Helicopters actually do NOT fly by thrusting/pushing air down, although that is, in part, a result of what is going on.  Helicopters create LIFT via the profile of the rotor blades and the angle of attack which varies according to operator input (at least on the bigger boys).  As I'm not a helicopter person, I don't know if tiny copters like the Mosquito can actually vary angle of attack, which makes the mechanism quite a bit more complicated.
If you look at a copter blade profile, it's generally the same as an airplane wing.  The faster it spins (and therefore moves through the air), the more LIFT is generated, and eventually enough lift is generated to lift/propel the copter.
A turbine engine provides THRUST, and it is the THRUST that lifts/propels things like Zapata's board.

"I don't know if tiny copters like the Mosquito can actually vary angle of attack" How else would it be controllable?

Lift is created by pushing air down. To create an upward force on the aircraft a downward force must be applied to air by principle of action and reaction and that pushes air down. And because momentum grows with speed linearly, but kinetic energy with its square, pushing more air faster requires less induced power. And the mechanism isn't that different anyway. The profile of the rotor and compressor blades is almost the same, just the rotor blades are few and long to push a lot of air a little and compressor ones are many and short to push little air a lot.


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Is there a way to integrate recorded digital media evidence into a pilot report?
If I encounter something during flight that I feel other pilots in the area at that time need to be aware of, the standard procedure is to file a pilot report.  If I have taken a photo or video of the phenomenon or incident, is there any way to integrate this digital media evidence file into the pilot report?  Can you type in website(s) link(s) to the digital media?

No. PIREP's follow a strict format that predates that kind of digital media. They must be compatible with distribution via AFTN and ACARS. PIREP's are created from a limited character set, and there is no way to attach any kind of digital media.

Not to mention that the time-sensitive nature of PIREPs renders digital documentation typically unnecessary and obsolete.


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Are there FAA approved infrared night vision devices we could use in case of engine failure at night in IFR conditions?
Terrible situation.  Your single engine on your general aviation aircraft fails.  You are flying at night, no airports nearby enough to land at and patchy fog causing Instrument Meteorological conditions near ground level.
You pitch the plane for maximum glide, squawk the emergency 7700 code on the transponder, declare an emergency, and try desperately to see an opening in the fog for a field or road to attempt an emergency landing but can't see anything as it is pitch black and foggy.  You follow the emergency procedure to try and get engine started.  In order to not harm civilians on the ground who had no role to play in your mishap, you ask for vectors from ATC to a shallow body of water.  ATC vectors you to a nearby small lake for you to ditch the plane.
Is there an FAA approved infrared night vision device that would have allowed me to see through the ground fog and locate a suitable landing site?  If FAA approved model does not exist, what is the minimum sensitivity and resolution that would do the job?

The recommended procedure is avoidance. Don't allow yourself to get into that situation of single engine night IFR over an area with ceilings that low.

In light aircraft, the current trend is to use synthetic vision, not night vision gear (which is very expensive and requires special training). It's available in panel avionics and tablet apps. Apparently it's good enough to land an aircraft, at least on a runway.

Why do you care about FAA approval in this case? Anything that helps you get on the ground alive is fair game, and allowed according to CFR 91.3(b). As long as you aren't using it for normal flight ops, it's fine.

Does IR pass through clouds?

@SteveKuo Depends on the frequency.  See  https://physics.stackexchange.com/questions/333854/which-frequencies-of-ir-and-uv-light-best-penetrate-the-atmosphere-with-least-in

By the way, ATC would almost never vector you to a lake, or any body of water, to ditch. Your chances of survival for a ditching, especially at night, are extremely slim. Especially with a small single engine GA with fixed gear, you will most likely flip over and drown. ATC may try to vector you to an airfield, or a highway, but beyond that they aren't going to pick your "landing" (crash) spot for you.

@Ron Beyer I was told otherwise by my IFR instructor.  Not necessarily being vectored by ATC, but as a sacrifice chosen by the PIC to avoid getting other people on the ground in harms way.  If you would like I can pose this topic as a separate question for more input.

I've flown NVGs in a helicopter where they were mounted securely to our helmets. We'd mount them prior to flight because trying to mess with them, even in normal flight with the other pilot on the controls, was an act of futility. Keep in mind, we trained heavily with these, hundreds to thousands of hours a year, and knew better than to try and set them up in the blackness of night in-flight. My point is I suspect you would do yourself more harm than good if you were in a situation like that, high anxiety, high stress, complete darkness, with time running out. With all the fumbling around, you


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How to fill out IFR flight plan for manned helium balloon flight into class A airspace with no predetermined route or destination and less crew?
Per FAA regulations, an IFR flight plan must be filed before going above 18,000 feet MSL as this is class A airspace.  How do we fill out the IFR flight plan if the destination landing site and the route taken of the lighter than air aircraft are unknown, and one of the crew members will be disembarking in flight and parachuting down?
Note: This operator does this on a regular basis.  They use manned helium lighter than air craft, not hot-air balloons as answered on previous questions so this question is not a duplicate.

You should be able to, with reasonable accuracy, determine your route. You can do this with winds-aloft and other meteorologic data.

Off track but before you get too far along, make sure you have a contract for He.  100% He is virtually impossible to buy now unless you have an established medical, research or industrial account which has been buying He, and the price is again going up, like it did 8 years or so ago.

@mongo if He gas cannot be obtained, is it possible to use hydrogen if all possible safeguards are taken?  Should I open as separate question?

That would be a good new question. I am not sure that all possible safeguards is adequate. Remember the Hindenburg!

I just helped a University launch of an unmanned balloon and I used an E-6B for completing the NOTAM for the launch.  GPS and tracking showed that the estimated path deviated from actual path by small numbers.
We were advised that no IFR FP was required for a small (~3kg payload) unmanned balloon, so none was filed.  We did advise center at launch, and with updates on the way up and down.
Addendum #1
After thinking about this, there are really two parts to this question. The part about route prediction I have addressed in part.  Keep in mind that gliders file IFR and they have little ability to climb higher on demand. The FP can provide an area, just like an IFR FP or and IFR clearance for aircraft can have block airspace, or even routing at pilot's discretion.
The other issue is whether a FP is needed. For manned balloons in controlled airspace, operating under IFR, the answer is clearly yes. But again, there is allot of latitude in what a FP can specify, and what clearance might be issued.
For unmanned balloons, which is where I have more experience, the rules are quite different.  And size is limited.
But again, the FAA can issue waivers, and they are done regularly for all kinds of flights. So just because the rules prohibit or do not allow, doesn't mean that a waiver could be issued to allow.

yes, but I do believe IFR FP is required for anything manned in class A airspace.  The regs don't mention any exemptions.

One can always ask for an exemption.

thx, SE is like a university to me.  Ask the right questions and keep learning.

Well, I wear different hats from time to time, as a research scientist,  a test pilot, a university professor, and even a CFI, but one thing I would caution you about, and that is reliance on forums such as SE.  While many answers may be entertaining, and quite a few might be correct, the peer review that occurs in this forum is predominantly based on popularity.  In other words, with less authority that established texts and even industry peer reviewed papers. The full question is seldom addressed, and only in limited space. So take care with what you read and then rely on.

My own above posting included, as I addressed only part of the question. Even with the editing, it is only a partial, informal, coverage of your question.

thx. I had someone sponsor me for researchgate.net but still fell through since I do my own research, unaffiliated with any organization. SE is a great resource but I always try to verify info gathered. Rather than ask here in a discussion, I would like to open a separate question about how to ask for waivers and exemptions in filing flight plans, unless you can point me to where the question has already been asked and addressed.

Do a search.  The FAA has pages on common ones like altitude and airshows.

I'm not sure if this is considered a duplicate question, but two previous answers appear to answer this question.
This previous answer partially answers your question, "Do hot air balloon pilots file flight plans?"
As for skydiving, you must remain in VFR with visual reference with the ground before skydiver exits. Is skydiving in IMC legal and safe?
I need to look it up but, I'm guessing a balloon in the clouds in Class A airspace might also need an altitude reporting transponder so ATC can provide separation to IFR aircraft. Nothing ruins your day like flying into a huge balloon in the clouds at 320kts in the flight levels.

Granted, it's probably preferable to flying into another heavier-than-air aircraft - those tend to be rather more solid.


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How does a helicopter rotor keep spinning in the same direction when autorotating without reversing the pitch
I have read that if helicopter's engine fails, you set the pitch to minimum but not reverse pitch. The rotor would have to be tilted back to provide an angle of attack on the blades so it glides like a fixed wing aircraft but with the rotor spinning to keep the blades from buckling under the weight of the craft. I think it would have to go into a slight reverse pitch to spin the same way. That would also provide more angle of attack on the receding blades where it is needed because of the lower air speed over those blades. How does it keep rotating in the same direction with the air going up through it if it can't go into a slight reverse pitch?

Related: How does Propeller windmilling work?

For a stable autorotation, the angle of attack of the driving part of the blades has to stay around 12º. But that's the AoA, and not the pitch... The AoA is the sum of the inflow and pitch angles, and the inflow angle is a function of the horizontal and vertical relative winds as 'seen' by the relevant blade section. If the inflow angle is high enough, you can have a convenient AoA for autorotation, even if the pitch is negative...        [img]https://i.imgur.com/DLy3Ffh.png[/img]

@Bianfable I didn't have a problem understanding windmilling. I just couldn't understand how it could rotate in the same direction when the wind was reversed, but not the pitch. From the answers I got, it seems to be due to the upward slope of most of the underside of the blades when the pitch is low.

Most rotors can go near zero pitch or slightly negative with the collective all the way down.  But the blades don't have to go to negative pitch to get driven forward by the airflow coming up through the disc. They just have to be at a low enough pitch for the resultant angle of attack of the blade to produce a lift force with a strong forward (thrust) component somewhere along the blade.
This is happening in the mid span area of the blade, where the lift vector has a significant forward tilt, like an airplane wing gliding. Toward the tip, the lift vector is up and slightly aft, like an airplane wing under power, and all the lift force is vertical, while near the root, the blade is stalled and the velocity is too low to do much of anything.
The key bit is lift vectors produce forward thrust in the "driving" region of the blade because the blade is advancing forward at an appropriate velocity and it's the resultant airflow angle of speed + pitch, not the the pitch angle itself. This is achieved at lower collective pitch angle than while under powered flight, but it doesn't have to be negative.
.

Wow, is the rotor blade really that "twisted"?  I'm comparing the chord line of the blade sections in the "driven region" and "driving" region diagrams, noting that the axis of rotation is the same same in each diagram.  Wouldn't essentially the same diagrams apply, still showing a greater aoa on the "driving region" and also a more forward tilt of the "L" and "T" vectors for the "driving region", all due to the difference in "inflow" direction (which is due to the difference in rotational speed), even if the blade had no twist?

The "effective twist" is a product of the velocity variation.  Imagine two sailplanes gliding past each other in opposite directions, and they hook wing tips and are forced to circle each other while gliding down. The hookup point has nearly zero airspeed and nearly 90 deg AOA. AOA will decrease out toward the tip as velocity increases until at the tip it's down to a few degrees. About where the fuselages are, the AOA will be a range and orientation that is able to keep propelling the glider forward in a glide, but forced to circle because you both foolishly added Velcro to your wing tips.

Re above-- ok, I see how the "inflow" (maybe not the best name as what is illustrated appears to be the resultant of the relative wind w/r/t helicopter body plus the forward velocity of the blade) comes from a very different angle at different points on the blade.  Due to difference in forward velocity of blade at different points.  Still doesn't explain why angle between chord line of blade and axis of rotation of blade which is represented as dashed line in diagram is so different between top and bottom of the right-hand diagrams.

Ah I see what you mean. Not sure.

@ Quiet flyer It would be easier to understand if the people producing these diagrams varied the angle of the relative wind flow, as that is what is different, and not the chord line which is the same in all sections. Also, I wish they wouldn't exaggerate the pitch. It doesn't show how the blade is propelled forward, as, at that angle, there would be no part of the underside sloping up toward the back, and the rotor would be driven backwards.

In the driven region diagram, if the chord line was horizontal when the pitch is set for gliding, the underside would slope up slightly towards the back, probably provinding enough camming action like a windmill blade, necessary to push the air back and get forward thrust (Newton's 3rd law). I am a devout Newtonian and don't believe it is possible without a surface pushing the air back (or pulling it back by Bernoulli effect). The way it is shown, the inflow at the angle it is going would continue backward after hitting the under surface but would only provide lift, not forward thrust.

John K's explanation is correct. However, It may be interesting to add some text and an illustration taken from a classic book, 'The Autogyro and how to fly it' By Reginald Brie (1935):

+1 for going to the trouble to scan the pages lol.

@ xxavier From your diagram & a picture of a real chopper, the blade cross section looks symetrical like an aerobatic plane wing, sloping upward on most of the underside, which would explain the forward slope on the lift vector. I had always assumed the blades were shaped like the bidirectioal wing with camber I described hear:"https://aviation.stackexchange.com/questions/19122/is-there-an-aerofoil-that-gives-reasonably-good-lift-for-both-air-flow-direction", and pitch set slightly negative when gliding, which would also give less AoA on the advancing blades & more on the receding ones. Thanks

Rotor blades were traditionally symmetrical airfoils, used because they had the lowest pitching moment, which is trying to twist the blade nose down toward the tip. Newer machines using composite blades with more torsional stiffness are able to use more efficient cambered airfoils.  The air isn't coming at the receding blade from behind. It's from below and kind of behind-ish, but with the rotational speed of the blade, the receding blade is still seeing the air coming at it from ahead and below, from the blade's perspective.

@John K When you said symetrical, did you mean front to back like the bidirectional wing, or top to bottom like anaerobatic plane wing. Also, in the previous PS above, I meant to say driving (inner) region. Does the air flow backward over it.

Symmetrical as in same curvature top and bottom, like an aerobatic wing designed for inverted flight. Look at an old Bell-47 blade cross section, and the blade on a late model design and it'll be obvious.

For ease of exposition, let's consider a helicopter simply hovering.
The typical airfoil along the blade sees a velocity $V$  which is the sum of two components:

an horizontal component $U$ due to the rotation of the blade
a vertical component $V_i$ called induced velocity which is (more or less) due to the downwash of the blade(s) preceding the current one in its rotation; this term is typical for a rotary wing but is not normally encountered on a fixed wing.

As usual, the airfoil generates a lift $L$ perpendicular to the airflow $V$ and a drag $D$ parallel to it. Their sum is the total aerodynamic force $R$. In the rotary-wing world, this aerodynamic force $R$ is more usefully decomposed into a thrust $T$ parallel to the shaft of the rotor and a force $P$ perpendicular to it. The thrust $T$ is the force keeping the helicopter in hover while the force $P$ is the one that the engine has to win to keep the rotor spinning:

Aerodynamic force $R$ generated by a rotor in hover invested by airflow at speed $V$
So far so good. What happens now when the engine quits? Nothing special. Due to its inertia, the rotor continues to rotate and nothing changes in the previous picture. Anyway, the force $P$ is now no more counterbalanced by the torque of the engine and therefore $P$ makes the rotor slow down. If the rotor slows down more than some 80% of its nominal rpm, the airfoil begins to stall increasing even further the magnitude of $P$ and leading to a no more recoverable catastrophic situation. The time from when the engine quits to when the rotor has lost most of its rotational speed is no more than a couple of seconds.
So the pilot has only a couple of seconds to reduce as much as possible $P$. How can this be achieved? Simply decreasing $\theta$ (by lowering the collective):

When the engine quits, $P$ must be reduced as quickly as possible to avoid the rotor to slow down too much and stall; this is achieved by reducing the pitch $\theta$ of the blade
Now $\theta$ and $P$ have become lower but $T$ as well. The weight is no more compensated for by $T$ and therefore the helicopter starts sinking with a vertical speed $V_d$ (investing the rotor from below upwards):

The rotor sink with a speed $V_d$ which flattens $V$ increasing $\theta$ and tilting $R$ forward
Note that the sinking speed $V_d$ makes $V$ "more horizontal" both increasing the AoA of the airfoil $\theta$ and tilting the total aerodynamic force $R$ a bit forward; this helps in reducing the component$P$. When $V_d$ is circa $>1.8V_i$, $R$ has tilted forward enough to have:

a component $P$ null; and
a component $T$ big enough to act as a parachute.

The helicopter has just entered the autorotation phase:

$V_d$ has increased so much that $R$ has become perfectly vertical: the rotor is in autorotation

Reality is, as usual, a bit more complicated but this simplified approach should help anyway to understand the autorotation manoeuvre.

From your answers, it seems to be the upward air hitting the upward sloping mid to rear underside of the blades as in the diagram below that keeps it spinning the same way with forward pitch and upward air flow, with lift provided by the air striking the bottom, and flowing over the top. Thanks fellows.

Coanda effect happens when a 1) turbulent 2) jet 3) blows upon 4) "half" of the surface of a 5) flat or slightly curved body. Except for very particular cases, coanda effect has normally nothing to do with aircraft. What happens in autorotation is simply that the composition of the sinking speed with the rotational speed gives a lift which is mainly vertical: the blade produces thrust with no torque (see the last picture of my answer).

Is that more like what happens? That should produce an upward & slightly forward L vector with the air deflected back at the mid to rear underside, and flowing around the blade to provide lift. If you rotate blade in your picture to the actual pitch, that's about the angle the air (V) would be striking the bottom.

@jkztd: water flowing on a spoon is not due to the coanda effect but simply due to "surface tension". Coanda effect relies indeed on the creation of vortices where it gets in touch with the surface and a consequent low pressure region.

It's a bit hard to distinguish the difference between Coanda effect and Bernoulli effect. My understanding is that the Bernoulli effect attracts the fluid to the surface by dragging away any fluid in between, and holds it there if the surface is curved, creating the Coanda effect. The little low pressure zone that creates the vortex after the step in diag. 5 Here "https://en.wikipedia.org/wiki/Coand%C4%83_effect" just helps to pull it down to the surface, and wouldn't be necessary if the opening was on the surface. I don't think NOTAR helicopters use that step.

The Coanda effect on the tail of a NOTAR helicopter, as well as directing the stream of air from the vents to the side to produce corrective side thrust, also attracts and deflects downwash from the main rotor, giving more thrust and increasing the bulk of air pushed out, reducing the energy wasted as slip like a larger propeller pushing a plane or boat forward more and the air or water back less.

@jkztd: If you want to see both effects on the same thing, get a glass ball, like a large marble. Put it in the sink & run a stream of water on it, then put the plug in. At first, it will be held in place by surface tension. Then, when immersed, it will be held by the Coanda effect. If you have an empty printer ink bottle with a spout, or a syringe, put some water in it & inject the inky water into the stream, then into the surrounding water. You will see the stream still follow the surface, then see the surrounding water drawn into it. Show your wife. I'm sure she'll be very interested!

@jkztd: I tried that test using a small plastic bottle with a long spout, but without much success. A vortex kept forming where the stream entered the water and distributed the ink around the ball. But I did have more success by injecting it under the water near the top of the ball and see it get sucked in and down around the side.


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ACN/PCN Reporting System - Tire Pressure
I have an Airbus A320neo WV054 and I want to operate at a RWY that has PCN 55/R/D/Y/T. Below is my aircraft ACN data as per the Aircraft Characteristics Manual.

Looking at the table I can see that my max ACN value (54) is below the PCN value (55) on a rigid pavement with a Subgrade Strength Category D, meaning I can operate with my Maximum Ramp Weight.
However, my Tire Pressure (1.44 MPa) is less than the Maximum Allowable Tire Pressure Category Y (1.25 MPa). Does this mean that I am Tire Pressure Limited and I am unable to operate at the given runway?
I've gone through the regulations and all they mention is to make sure that PCN does not exceed the ACN value, and nothing about the Tire Pressure limit. Thank you.

1.44 is less than 1.25???

no, it is not less, but more...


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Can a deployable ILS operate in CAT II or CAT III?
Can a deployable ILS operate in CAT II or CAT III? As far as I know a deployable ILS can operate only in CAT I.

This article only states Cat 1.  Deployable ILS project has been ongoing for 7+ years, so -1 to you for not posting anything relevant about it in your question.

The D-ILS is to provide a system of equal performance to existing Category I fixed-based systems that provide aircraft guidance on final approach in low-visibility and low-ceiling weather conditions.

https://www.militaryaerospace.com/articles/print/volume-27/issue-11/rf-microwave/thales-developing-deployable-instrument-landing-system-for-air-force.html
March 2010 article on expected May 2010 Request For Proposal release:

The final RFP is anticipated to be out in May with source selection in June, and an award by December. Initial operational capability is scheduled to occur in early 2013.

http://www.aero-news.net/index.cfm?do=main.textpost&id=c873f7b8-2dd6-408f-9da2-b85f5b36a7ea
Here is another that says it is available in a transportable configuration and says it can do Cat II.  Is it available?  I don't know, the AF seems to be buying the Thales version currently.

Transportable and permanent configurations
Meets icao cat II ILS specifications
For Ground Controlled Approach (gca) operations, the ILS provides
controllers with par-like displays for up to four aircraft. All ILS glide slope
and localizer signal parameters comply with icao Annex 10 standards
for Category II ils, including accuracy, integrity, displacement sensitivity,
clearance, alignment, modulation and frequency. The fixed-based ILS has
been approved by the faa for use in the National Airspace System.

http://www.anpc.com/wp-content/uploads/2011/08/ILS-ANPC.pdf

Thanks,  the ILS CAT definiton is linked non only to the electronic part but to the overall integrated system (including antennas, cabling,) as  is linked to the probability of a critical failure during the landing final phase. In case of a deployable ILS  system( antennas not fixed to a  concrete basement and  stabilized and bracing, RF cables not located in cableducts, the probability of a failure is higher than for a fixed installation  and that's why a deployable ILS is  only for CAT I. What i can't find is any doc, advisory, rules issued by a  regulatory body (ICAO, FAA,..) about.

@massimosanvito: I believe what you're looking for is §3.1.3.11.3.1 and next of Annex 10 to the Convention (here for LLZ).


text:
What is the main reason why cruise flight in the transition layer is prohibited?
What is the main reason why cruise flight in the transition layer is prohibited? For example if we have a separation of 1000 ft between transition altitude and transition level, why should we not maintain a level in this layer of 1000 ft?
I know about transition altitude and transition level but what is the cognitive reason of this rule?

I mean there is a rule all we know..for example if we have a separation of 1000 ft between transition altitude and transition level ,why we should not maintain a level in this layer of 1000 ft?

OK, I rephrased your question and included your example from the comment. Feel free to edit again, if I got something wrong...

Thanks@Bianfable

Well, if you’re changing altimeter setting when transiting the level, what altimeter setting would you use when levelling off? What if someone else levels off, too, but with the other setting? How would you maintain separation to adjacent levels?

@CptReynolds-Thanks but what if we manage all traffics with the same altimeter setting ,as example both set QNH in transition layer and commence cruise flight,does it lead to problem?

The main reason for the transition layer is to assure separation between the highest usable altitude (TA) and the lowest usable FL (TRL). That means it has to be at least 1000ft thick.
If the QNH is 1014 or above the transition level is always just 1000ft above the TA (5000ft and FL60) because the whole FL system is shifting upwards above the MSL. This means for each hPa above standard QNH 1013 your transition layer will be about 30ft thicker.
If QNH drops to 1013 or below the opposite happens: The base of the FL system falls below MSL, so FL000 is at -30ft MSL per 1hPa below 1013.
If QNH is 1003, the difference between 5000ft and FL60 is only 700ft because 1000ft-(10hPa*30ft)=700ft. In this case the TRL above TA 5000ft has to be FL70 to assure the separation between highest altitude and lowest FL is at least 1000ft.
So now we have a transition layer with one spare FL - FL60. If one would now fly at 6000ft we only have the above mentioned 700ft to FL70; if one would fly at FL60 only 700ft to 5000ft. This is why the transition layer may not be used for cruise flight

Thanks @pcfreakss ...may I know conditions of assigning TA?

but assigning the TA is conventional actually , i wanna know does it deal with the separation between obstacles and ACFTs or not?

@Hamid The TA is published for a specific airport in the AIP and the ATIS. In Germany for example it is always 5000ft

@pcfreakxx It is actually 5000 ft AMSL or 2000 ft AGL, whichever is higher. See e.g. here.

Your question says there is 1000ft between the TA and TL, but depending on how QNH compares to QNE from day to day and from place to place, the actual thickness of the layer will vary; it will always be at least 1000ft (though rarely more than 1999ft). This guarantees that an aircraft at the TL and an aircraft at the TA will always be properly separated.
Flght levels (QNE) below the transition level (TL) could be less than 1000ft above other aircraft below the layer. Therefore, they are invalid.
Altitudes (QNH) above the transition altitude (TA) could be less than 1000ft below other aiircraft above the layer. Therefore, they are invalid.
Ergo, within the layer itself, there is neither a valid flight level nor a valid altitude; there is literally nothing in between for ATC to assign. You can only climb or descend through it to a valid assignment on the other side.
If you did try cruising at an invalid altitude/FL within the layer, then you would likely not be properly separated from crossing aircraft either at the TA, at the TL, or both. It's better for everyone to not have to worry about such things, which is why the layer exists in the first place.

Thanks a lot , but assigning the TA is conventional actually , i wanna know does it deal with the separation between obstacles and ACFTs or not?

@Hamid I've improved my explanation of aircraft separation. Terrain clearance is a concern any time you're at or below the transition altitude; that's usually how the authorities decide where to put it.


text:
Why does my data collected for wing area vs. horizontal displacement not correlate with known theory?
Based on my research, as the wing area of a glider increases, so should the flight distance. However, as you can see from the screenshot below,
The flight distance generally decreases when the wing area is increased. (I did 7 different wing areas and 5 trials for each wing area so 35 trials total, the data points in the picture are the averages.)
For context, this is for my IB Physics HL IA, and I was told that I need to find a positive linear relationship between the two variables. Is this necessarily true? Or can I have data that is negatively linear but then I justify it in my analysis? Theoretically, my experiment should have a positive linear relationship since I change the wing area and then measure the corresponding flight distance.
I have kept the following variables constant:
Weight of the glider at 27g
Launch angle from the ground at 8º, since I used a wooden platform with a thick rubber band.
Launch force of 30N
Windless sports hall
Aspect Ratio of 5
Please help me figure out what is going wrong, and how I should proceed. Thank you very much. I am a first-timer on aviation stack exchange so I hope my question makes sense.

Yes please, I would certainly appreciate enlightenment on the theory.

How did you get those points? Are they based on some real data, simulations or on simple estimations?

What else changed as the wing area increased? Weight? Frontal area? Aspect ratio? Center of Gravity? Many relationships apply when all else remains the same; when all else doesn't remain the same, then you can have competing influences at work, and your results are the sum of all the effects, not just the one that you're most interested in.

Let's see...  mass is 27grams, starting launch force is 30Newtons.  Hmmm....

I kept aspect ratio constant, weight constant, everything constant, except that the ratio of the wing area to the fuselage length and tail length changed...although I don't know what that does

@ThomasPerry...uhm are you trying to say that the force is too great for the mass?

@sophit, they are based on real data. I made the wood balsa glider myself and actually flew it in a real sports hall in real life.

Well, then post some pictures

@Midnightakatsukireborn Doing the math F=ma, the resulting a seems a bit unrealistic. My initial reaction was Wow!  That leaves me wondering if I have misunderstood something, or if there was a conversion error in the experimental data reading/reduction process.  As I recall, 1 Newton is equal to the force needed to accelerate 1 kg through 1 meter in 1 second, per second.  Your comments have been very helpful, indeed.  I surmise your y variable is distance, x is wing area...  no? An interesting investigative experiment and question that you have posed. Nice!

Yep, 30 Newtons looks ok, I think.

Yes, y variable is distance, and x variable is wing area! I'm sorry that I did not make it clear in the graph. Thank you for your encouragement and the comment to digiovanni, you guys are really awesome

Also, @sophit, sure, I'll post!

If one keeps the launch angle and force constant and increases wing area, the tendency will be for the model to fly higher, then stall, leading to a shorter gliding distance.
Hand launching gliders for distance from the ground is an art unto itself.
To better understand gliding, one may be way better off launching them from the grandstands rather than the floor so the model can reach steady state airspeed, where airfoil lift/drag properties can be studied.
Here you will find that optimal wing area corresponds to best angle of attack from the lift equation:

weight = lift = $\rho$ × area × V$^2$× coefficient of lift

Angle of attack is part of coefficient of lift.
If the wing is too large, lower angle of attack (for the same lift) will be less efficient and drag will be higher.  If the wing is too small, higher angle of attack will again be less efficient.
This relationship can also be studied based on airspeed, again by varying pitch settings.  Each wing will have an optimal L/D ratio, which gives the longest glide$^2$.
Keep weight constant, and adjust elevator trim (pitch) for larger and smaller wings accordingly.
For a given weight and airfoil type, an optimum size should give the longest glide$^1$.
$^1$ Reynolds number is also an important consideration.  Smaller, slower model airfoils will have different lift/drag performance characteristics as compared with faster full scale wings
$^2$ This data will make for some great graphs!

Hey, thanks a lot!! I think I have a better understanding now. Do you think I should redo the experiment to fly it from a grandstand or some kind of elevation? Also, just to clarify, I used a launcher (platform with rubber band, sloping upwards at 8º, and the rubber bands act kind of like a catapult). I did not hand launch. Thanks a lot again! Also, for your footnotes, do you mean the data I already have? If so then I'll happily continue writing my IA :))

@Midnightakatsukireborn yes, gently hand launching it (as close to its flying speed as possible) from elevation.  You may find that it is important to scale the tail to the larger wing.  As your technique improves, relative standard deviation for your flights will get better.  Catapult launched "free flight" gliders (uncontrolled) have many variables, ones dropped or gently launched from elevation quickly settle in to their flying speed (if they are staticly stable).

Another reference: for static stability

Ah, I see. However, I don't have the time to improve my hand-throwing technique, I need to write about the variables that I kept constant so...it will be pretty hard to convince IB that I was able to throw the glider without any human error (in any case I can't quantify human error). Dropping it seems like a good idea, but my sports hall has no area where I can drop it from, It's just flat ground with 4 walls and that's it. I can't experiment in the open otherwise there's too much wind. But thanks for the enlightenment!

@Midnightakatsukireborn You've made a good effort! Your experiment appears to be supported by your results.  Use your best form in the write up.  Nothing seems wrong with your hypothesis and consequent data.  Like most experiments, there is always concern something is wrong.  But you've checked, and re-checked, and thought-it-through... Remember to comment regarding possible sources of error, and consequent limitations in your results. DiGiovanni thinks much better on the right track about these things...


text:
Is it possible to power a B-52 bomber with four bypass turbofan engines?
Is it possible to power the B-52 Bomber with 4 bypass turbofan engines instead of the eight in its current configuration? They would have less noise and be a lot more fuel efficient.

https://www.defensenews.com/video/2019/06/20/heres-how-the-air-force-wants-to-re-engine-b-52-bombers/

A four-engine configuration has been proposed at least two times but would require expensive modifications to the wings.

A 2017 Flight global report, Rolls Royce offers BR725 for B-52 re-engine effort, said

So far, the USAF has foregone plans to reconfigure the B-52s with four engines, which would have required expensive modifications to the wings, R-R says. R-R previously considered a higher thrust variant of the RB211 turbofan engine as a four-engine option on the B-52, but the service does not appear to be moving in that direction, according to R-R.

A 2014 Aviation Week report, B-52 Re-engine Resurfaces As USAF Reviews Studies, said

Pratt & Whitney studied the idea in 1982, with four PW2000-series engines. In 1996 Boeing and Rolls-Royce jointly proposed to fit B-52s with four RB211-535s, with the government leasing the engines. The first plan was not taken up because all B-52s were to be replaced by B-1s and B-2s by the late 1990s, and the second failed because of resistance to leasing combat assets and a flawed economic assessment by the Air Force.


text:
Can compressor blades be made larger to increase thrust and efficiency?
Given the compressor section of the engine needs to move much faster and given the larger the blade, the larger the tip speed, would larger compressor blades produce more thrust and therefore better efficiency?
If not, what limits their tip size? Is it the torque of the hot sections of the engines, or to prevent a stall or flameout at the hot sections of the engines?

I would seriously recommend you attend aeronautical engineering classes or at least invest the time and read relevant text books. That would answer almost all your questions asked throughout the last weeks. I‘m sure you have good reasons and great ideas to feed all your questions, but what comes across to us readers/participants on this site is astonishingly similar to my five-year-old being let loose on aeronautical engineering - seemingly random, quick-fire questions without any background information given or own workings, let alone research demonstrated. I’m sure you are capable of more!


text:
Are there any regulations preventing one from converting an originally cargo aircraft to ferry passengers?
Are there any regulations preventing one from converting the cargo version of the Airbus A380 for passenger use?

Which country's regulations are you asking about? And see this question for the point about screens instead of windows.

I removed your background commentary on screens because it seems irrelevant to your question (and as I already commented, we have an existing question on that topic anyway). But if you think it really is important for the question then of course please just roll back or edit again.

Airbus would have to build one first - https://www.flexport.com/blog/airbus-a380-no-cargo-equivalent/

Converting a freighter to an airliner would require lots of work:

you have to install an HVAC system capable of supporting hundreds of passengers, which means installing air ducts from the engines to the cabin, etc. Major surgery to the wing and fuselage.
you have to install a sufficient number of doors and emergency exits (with associated systems). Major surgery to the fuselage.
big changes to the electrical system to support e.g. entertainment for the passengers.

So the conversion would require taking most of the aircraft apart.

There is no cargo version of the A380, but for other types:
There are no regulations prohibiting converting a cargo aircraft to a passenger one. It will just need to meet all of the passenger certification requirements, such as evacuation times, seat and structure crashworthiness, oxygen systems, and so on.
I don't think this has ever been done because it is extraordinarily expensive. It is cheaper to convert a passenger aircraft to cargo because for the most part you are removing items instead of installing them. Passengers also prefer new aircraft, so after going through the cost of converting the aircraft you'll struggle to fill it with people.
Can cameras replace windows? From a legal standpoint I'm not sure, I think yes as I recall a patent for it, but that would be an interesting question to ask here.

For the windows it is preferable to be able to see the outside before opening a door (in case there is an obstacle such as a fire preventing from evacuating from that side), even if all systems, including camera and screens, have failed (as expected in an emergency situation).

Normally the retrofitting path is from passenger service to freight service. In my experience, many freight operations already have the necessary airpacs, as certain cargo (zoo animals, livestock, biologicals and chemicals) may require environmental control.
The cost comes in outfitting the aircraft for people, with the accouterments of modern air travel.
There are options for convertible interiors which will handle freight and can be rapidly converted to passenger use, and these are particularly popular with operators in under served areas which have lower volumes.  The convertible interiors can be switched out in very short times (less than 30 minutes) and are suited for operations where people are moved by day, and freight by night.
One larger effort will be in electrical needs for the cabin and associated lighting and electronics.
Without checking the US regulations, it is not clear to me that windows are a requirement, except for certain stations.  Some configurations, such as medvac, may use few windows.  Some prison transports are done with windowless (or nearly so) passenger aircraft.
Different freight has different risks.  For example one carrier found that giraffes tended to munch on cables and wiring in the ceiling, requiring protective coverings on subsequent carriage of those animals.  Those freight mitigations could increase some costs.
Generally, cargo aircraft have adequate doors, as well as larger doors to the upper decks.  The bulk of the retrofit is seating, bins, environmentals (lighting, O2, air distribution) and seat rails.  It will depend upon the aircraft, but the retrofits do not usually involve major airframe work, although the cost may be high.
To answer the specifics on an A380 conversion, one would have to study the type certification and the delivery configuration of a given aircraft, and then analyze the requirements to move to dedicated passenger service.


text:
Why isn't transition altitude standardized in Europe?
In the US, the transition altitude is standardized at 18,000ft, however in Europe it is different for every airport.
Why is it not standardized like it is in the US? I could see situations where someone has their altimeter calibrated differently, and thus giving different altimeter readings, which would seem dangerous, especially for smaller GA aircraft that might not have TCAS?

It seems that there is US and Canada in one side, and "Europe and much of the rest of the world" one the other side. Quite strange given that feet is used because of the US influence

For starters, US is a country, Europe is not.

Can you give an example where non-standard transition altitude would be a problem?

Say aircraft A reads 5,500 ft, with altimeter set to standard, while aircraft B reads 6,000 with altimeter set to local, but if aircraft B was set to standard it would also read 5,500. A situation arises for whatever reason where the two aircraft are headed towards each other. The pilots think they're 500ft apart, but they really aren't!

TA is not "different for every airport". Some countries have a common TA used throughout the country, others have defined areas within which a certain TA is used.

@J.Hougaard even so, then say these two aircraft are near the edges of these defined "zones", and the previously defined situation occurs

@lightbord That generally won't happen, because TA's don't change any where near large airports. Even so, air traffic controllers know how to handle this, and will have procedures to ensure vertical separation in areas with different TA's.

You're right that having a common transition altitude is better- efforts are underway in Europe to set a common transition altitude. Multiple studies have been carried out by Eurocontrol and it has been noted that it is better to have a single transition altitude. For example, from an aircrew prespective:

The multiplicity of transition altitudes and the national rules and procedures make the European environment  very  complex.  This  can  lead  to  a  lack  of  altitude  awareness  and  altimeter  mis-settings  and  is  operationally  unsatisfactory.

and

Establishment of a common transition altitude has a clear safety benefit.

Similarly, from the ATC perspective:

The establishment of a common TA for ECAC States and the EUR Region is a  fundamental element in achieving the goal of a unified sky and the safety policy of reducing risks to the greatest degree practicable.

The reason such an unsatisfactory state of affairs have persisted is that people have become used to that- the second document makes that point:

ATC providers, as is human nature, grow comfortable with what they are most familiar.

The main reason is that there is no requirement for any common transition altitude. The relevant ICAO document simply states:

2.1.2.1    A transition altitude shall normally be specified for each aerodrome by the State in which the aerodrome is located

and

2.1.2.3    As far as possible, a common transition altitude should be established: ...

As a common transition altitude is not exactly a requirement (in-spite of its advantages) different European states have historically established their own TAs, to be decided by the aerodromes or the regulatory authorities.
As they have become comfortable using it (and no major accidents have happened because of this), there is no serious move towards the establishment of a common transition altitude (through arguably, this is the case with much of the world- common transition altitude is not that common). In the UK, CAA has launched a consultation process to raise the transition altitude to 18,000 ft, which notes that,

... it has been agreed that the TA in the UK will be raised to 18,000ft.

'A common transition altitude is better' better than what, and for whom? I am not sure it is.

@DeltaLima better for avoiding confusion among pilots and ATC. Say you're in an area where the TA is 7000ft, and moving into an area where it is 7500ft. You're at FL70, but due to a severe pressure your actual altitude is 7600ft. Now you report in "blahblah with you FL70", ATC is confused as they see you at FL75.

@jwenting If you are FL070, ATC will not see you at FL075, but perhaps at 7500ft. But that is not my point. Take for example the Netherlands: maximum elevation is approximately 1000ft AMSL, the highest obstacle is approx. 1500ft AMSL. The transition height is 3000ft for IFR, 3500ft for VFR. The aircraft in your example would both be flying at standard pressure setting. If the transition altitude would be raised to 18 000ft, both aircraft may have had different settings if the pressure in the area's would differ. A higher TA would cause more workload and more potential for errors.

It is the pilot’s responsibility to know what the TA is where he is flying. Typically it is a fixed value for an entire FIR and/or country, which makes this relatively easy.
There is a buffer of at least 1000ft between TA and TL specifically to prevent the safety issue you describe (including allowable altimeter errors). Also, ATC’s terminology will tell you whether to set QNH or QNE, even if you didn’t bother to look up the TA as you should have. So, varying TAs simply isn’t a significant problem in practice.
While it would seem marginally easier for everyone to have a common TA, that disregards the reason why different TAs exist in the first place: terrain.  A low, flat country can reap the benefits of a low TA, for both pilots and ATC, while a mountainous one can’t.
Also, not all of the “US” has a TA of 18kft. The US-managed Oceanic Control Areas, which aren’t that far offshore and include part of the Caribbean, have a TA as low as 6kft; there’s no reason for it to be higher over the oceans where there is no terrain to worry about—and often no available altimeter setting to safely fly below the TA, so the low TA allows a low TL and thus more controlled airspace for IFR flights.


text:
In modern commercial aircraft, is it possible for pilot inputs to exceed the tolerable structural loads?
It seems that modern fly by wire systems should / could limit pilot inputs to prevent structural damage.
For example, American Airlines 587:

From the NTSB report of the accident:
The National Transportation Safety Board determines that the probable
  cause of this accident was the in-flight separation of the vertical
  stabilizer as a result of the loads beyond ultimate design that were
  created by the first officer’s unnecessary and excessive rudder pedal
  inputs. Contributing to these rudder pedal inputs were characteristics
  of the Airbus A300-600 rudder system design and elements of the
  American Airlines Advanced Aircraft Maneuvering Program.

relevant: https://aviation.stackexchange.com/q/149/1467

Welcome to the site! I don't really understand what your question is: the title asks if loads can be exceeded, and the text gives an example where they were. Can you edit your question to make it clearer what you want to know?

No the question is clear, the concerned aircraft is old fashioned compared to modern aircrafts such as B 787 , A350 etc

Airbus fly-by-wire aircraft have what is called envelope protection which is to prevent pilot inputs from exceeding structural limits as well as keep them from getting the aircraft into an upset flight regime (stall, overbank, etc.). The philosophy behind it is that, if the pilots need to perform an extreme maneuver they can be as aggressive with the controls as they want, confident that they won't break the plane.
Boeing generally disagrees with this approach saying that, in an emergency, the pilot needs to have all possible force at his disposal, even if it breaks the plane. See the question Federico linked to in comments for more on this.
Of course, the Airbus system can only provide these protections when systems are all functioning properly. If part of the system is not working the protections are removed. Examples: AF447, XL Airways 888T, Indonesia AirAsia 8501,
As far as AA587, the A-300 is not a fly-by-wire aircraft and doesn't have envelope protections. It's debatable, though, if envelope protection would have helped in that situation. None of the rudder inputs by itself was outside of the structural limitations of the aircraft so the computer would probably not have prevented them. The failure was due to the pilot making alternating inputs in quick succession which caused the sideslip angle to build up to twice the certified design strength of the vertical stabilizer. The A300 system was designed to limit the rudder travel available as speed increased, which is probably fairly similar to what the fly-by-wire computer is programed to do in other Airbus planes. But it would be difficult to determine what complex combinations of inputs might exceed the limits and prevent them.

The repeated rudder doublets didn't rapidly fatigue the vertical stabiliser; they drove the aircraft to increasingly-large sideslip angles that eventually became great enough that the last doublet produced enough aerodynamic loading to snap the stabiliser off the plane.  The stabiliser didn't separate until it was subjected to loads sufficient to remove even a brand-new vertical stabiliser.  Source: the official NTSB report.

@Sean Thanks. Edited answer to reflect that.

No Boeing does not disagree with this approach, with the 737 max accidents the pilots had no force at their disposal, the faulty software killed the passengers and the crews. Boeing and airbus are in phase in their approaches. The difference is that Airbus introduced FBW ahead of Boeing.

Same thing with rudder doublets happened with this crash, https://www.baltimoresun.com/news/bs-xpm-1993-04-18-1993108262-story.html

@user40476 This answer was written before the 737max. Boeing has changed their approach over time. They even make fully FBW aircraft such as the 777 and 787 although I'm not certain as to what type of envelope protections they have.

@TomMcW, I am not saying that Boeing introduced the FBW with the MAX, I am aware the B777 is fully FBW including the rudder except partially for few spoilers, the approach is presently the same since the direct mode without protection is just artificially  direct because it is computers dependable  for both manufacturers. I am just saying that Boeing does not disagree with this approach, even though  they disagreed until they found it more economical, may be too much economical with what they did on the MAX

Doublets effect can’t be avoided with cabled pedals, so their  effects couldn’t be avoided even with early FBW aircraft, because on these the rudder was partially cabled with corrective FBW actions.
Today, AIRBUS and BOEING have full FBW authority on the rudder, doublets are dampened by the software and the structure is protected.
These protections do apply to all surfaces with modern  aircrafts within certain human factors limits.
Any apparent authority of the pilots over the system is via the software,
in Airbus technique this authority is active in case of degraded conditions, I.e. alternate or direct laws instead of normal laws.
With Boeing modern aircrafts pilots full authority is activated too when the system is degraded or on manual selection, but all this via the software, no more conventional mechanical cables are used on flight controls

A fly-by-wire system is going to be controlled by software. All software has bugs and conditions that it is not designed to handle. Thus, even in a fly by wire system it is possible for the control inputs to exceed structural loads.

Is this an answer to the question or a comment?

Can you not read?

« All software has bugs and conditions that it is not designed to handle ». Any general proof?